It has been known for many years that African Americans experience twofold higher rates of hypertension (Htn) than do whites. The underlying biological mechanisms which lead to this differential are still not understood, however. Despite widespread speculation that persons of African descent are genetically susceptible to Htn, few direct studies have been carried out. In this project the investigators propose to investigate familial patterns of Htn and related CV risk factors in the United States and Nigeria. Rates of Htn remain low in West Africa, and this study will provide a contrast between populations of similar genetic background in a low versus high risk environmental setting. 240 families will be identified from recently completed community surveys in Maywood, Illinois and Ibadan, Nigeria. Probands will be ages 45-55 and equally divided between males and females. A minimum of five first- degree relatives will be examined in each family to obtain information on the following variables: blood pressure (BP), obesity, urinary sodium and potassium, socioeconomic status and physical activity. In addition, plasma and DNA will be collected and stored for future studies of relevant physiologic intermediate phenotypes and candidate genes for Htn in the two contrasting populations. These data will provide the basis for examining familial aggregation of BP/Htn and related CV risk factors. Three primary goals will be addressed: 1) to determine whether the familial aggregation of BP in black populations is influenced by the overall distribution of environmental factors at the population level, by contrasting the distribution of familial correlations of BP and the familial aggregation of Htn, in Nigeria and the United States; to determine the significance of measured environmental correlates of BP by comparing the magnitude of variance components for probands and relatives in each setting; and 3) to use path analysis to obtain estimates of genetic and cultural heritability of BP, controlling for clustering environmental factors at the household level. Plasma and DNA samples collected in this study will provide additional valuable resources for future molecular research.